A subspace equaliscopic system was a device that jammed subspace communications in a two-parsec radius. It was able to tap directly into the solar wind so that it could operate without the need for a crew. However, the ability to operate unmanned camed to a heavy price: it needed a sublight-only starship with a large solar sail or a large amount of solar panels.
The USS Boston once attempted to sabotage the test run of the SES conducted by Starfleet. (TOS video game: "Starfleet Command (game))
The Interstellar Concordium Pacification Army operated a SES in the Thuban system, housed in a Starstreak-class freighter. It was finally destroyed after more than a century of continuous, unmanned operation, by attack fighters launched by the USS Antechrist. The ISC version needed only 10 gigawatts to operate. (Star Trek: False Vacuum: "Structural Unemployment")